Bump rackup from 1.0.0 to 2.1.0

Bumps [rackup](https://github.com/rack/rackup) from 1.0.0 to 2.1.0.
- [Release notes](https://github.com/rack/rackup/releases)
- [Commits](rack/rackup@v1.0.0...v2.1.0)

---
updated-dependencies:
- dependency-name: rackup
  dependency-type: indirect
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -390,18 +390,18 @@ GEM
     puma (6.4.0)
       nio4r (~> 2.0)
     racc (1.7.3)
-    rack (2.2.8)
-    rack-protection (3.1.0)
-      rack (~> 2.2, >= 2.2.4)
+    rack (3.0.8)
+    rack-protection (3.0.6)
+      rack
     rack-proxy (0.7.7)
       rack
-    rack-session (1.0.1)
-      rack (< 3)
+    rack-session (2.0.0)
+      rack (>= 3.0.0)
     rack-test (2.1.0)
       rack (>= 1.3)
-    rackup (1.0.0)
-      rack (< 3)
-      webrick
+    rackup (2.1.0)
+      rack (>= 3)
+      webrick (~> 1.8)
     rails (7.1.2)
       actioncable (= 7.1.2)
       actionmailbox (= 7.1.2)